High pressure and high flow valves are used in a variety of applications. For example, clinical laboratories and hospitals utilize various diagnostic apparatuses to analyze patient medical samples, such as blood, urine, other fluids, and tissues. In such apparatuses, high pressure and high flow valves control the flow of reagents, buffer solutions, washouts, and other requisite fluid components that are used in the analytical processes. Often, the diagnostic apparatuses employ manifolds with micro wells incorporating multiple valves for controlling the flows of differing amounts and/or types of fluids. Because it is desirable for a diagnostic apparatus to be as compact as practicable, size of the valves remains a concern, but with reduced size sufficient speed and efficiency needs to be maintained.
Reduced valve size has several advantages, so long as efficient sample throughput at a reduced cost is achieved. Reduced valve size, and particularly valve width, permits an instrument configuration in which multiple valves are mounted adjacent to each other over micro wells on a common manifold to maintain a compact footprint, and to organize fluid connections efficiently. Smaller width valves allow for reduction in the manifold size, which contributes to decreasing the overall instrument size. The reduced valve size also permits reduction of the size of fluid paths, which decreases fluid use which is important when expensive reagents are employed. Systems using smaller bore tubing of the flow paths require higher system pressures to deliver the needed flow rates. Reduced system volume combined with the desire to process samples faster results in higher system pressures. From a valve perspective, this translates to a need to generate higher actuator forces while reducing width.
Solenoid valves with an electromagnetically driven actuator may be employed in high pressure and high flow applications. Higher flow and pressure capabilities typically require a larger valve actuator to develop the sealing force needed for valve operation, which poses a significant challenge in balancing size and performance. To achieve higher flow, a larger orifice is required, and consequently a larger stroke to allow full flow to develop. However, this requires more magnetic attraction force from the actuator to overcome the large air gap.
Some improvement in the magnetic attraction force that drives the actuator can be made through magnetic material selection, but the performance difference between materials that are readily available and cost effective is limited. Additional improvements in attraction force can made through increased coil power and number of wire turns, but there are diminishing returns once the soft magnetic materials have been saturated with the magnetic flux, and peak power budgets must also be considered. Increasing cross-sectional area of the flux path components allows more flux to be carried and thus increases magnetic attraction force, but this must be balanced against the desire to reduce the valve size, and the valve width in particular. Accordingly, it has proven difficult to reduce valve size while maintaining efficient performance at the requisite high flows and pressures.